Zoo-352 Principles of genetics Lecture 4 Mitosis
Overview of mitosis Mitosis is a part of the cell cycle process by which chromosomes in a cell nucleus are separated into two identical sets of chromosomes, each in its own nucleus. Mitosis is divided into karyokinesis (division of the nucleus) and cytokinesis (division of the cytoplasm). The sister chromatids are held together at a specific region of the chromosome called the centromere. Mitosis is a continuous process and occurs only in eukaryotic cells particularly in non-sex cells (somatic cells). Prokaryotic cells divide by a different process called binary fission. Mitosis is divided into four stages: prophase, metaphase, anaphase and telophase (Greek: pro-, before; meta-, mid; ana-, back; telo-, end). The timing of the four stages varies from species to species and from organ to organ.
The phases of Mitosis 1- Prophase:
The phases of Mitosis 2- Metaphase The spindle fibers are form and each centromere attached to a kinetochore microtubule from each centrosome. The two centrosomes begin pulling the chromosomes towards opposite ends of the cell. The resulting tension causes the chromosomes to align along the metaphase plate.
The phases of Mitosis 3- Anaphase Anaphase begins with the two sister chromatids separating and moving toward opposite poles on the spindle fibers. The sister chromatids are joined together by cohesins. The degradation of cohesin at the centromere allowing the sister chromatids to separate.
The phases of Mitosis 4- Telophase In animals, cytokinesis is first apparent by constriction between the two poles. In plants, a cell plate grows in the approximate location of the metaphase plate.
The phases of mitosis in onion root tip cells
Significance of mitosis 1)In multicellular organisms, mitosis produces more cells for growth and repair. 2)In unicellular organisms, mitosis is a type of asexual reproduction.
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